The present invention relates to an improvement in a fault diagnosis system for automotive electronic devices.
A known fault diagnosis system for automotive electronic devices and its drawbacks will be described with reference to FIG. 1. Referring to FIG. 1, an automobile has electronic devices each having a self-diagnosis function and constituted by a controlling microcomputer, memory and other devices. The automobile also has sensors 2a, 2b and 2c which sense the operating conditions of various parts of an automobile and produce signals indicative of the sensed of operating conditions actuators, 3a, 3b and 3c operate in accordance with signals produced by the electronic devices 1a, 1b and 1c to control the operating conditions of the respective portions of the automobile. The automobile also has a connector 4 which is supplied with output signals from the electronic devices 1a, 1b and 1c. A warning lamp 6, is connected to the electronic devices 1a, 1b and 1c. These constituent elements of the fault diagnosis system are mounted on suitable portions of the automobile.
The diagnosis system has a fault diagnosis tester 5 which is connected to the electronic devices 1a, 1b and 1c through the connector 4, when it is desired to diagnose the states of the electronic devices. The tester 5 has operating keys 5b for reading data from the electronic devices 1a, 1b and 1c, and a display 5a designed for displaying data read from the selected electronic unit together with a code which identifies the electronic device.
As stated before, each of the electronic devices 1a, 1b and 1c has a self-diagnosis function so that it can sense any fault in its associated peripheral devices, i.e., the sensor and the actuator. The electronic device 1a, 1b or 1c, which happens to sense a fault in its associated peripheral part, stores in its memory (not shown) a code representing the faulty portion and data indicative of the fault, while turning the warning lamp 6 on. More specifically, the warning lamp 6 blinks as a switch (not shown) is turned on, and the number of blinks of the warning lamp is controlled in accordance with the code stored in the memory of the electronic device. It is therefore possible to find the faulty portion by counting the number of blinks.
For the purpose of conducting a diagnosis, the fault diagnosis tester 5 is connected to the electronic devices 1a, 1b and 1c through the connector 4. The operating keys 5b are operated in a predetermined sequence to successively select an electronic device 1a, 1b and 1c by inputting the code representing the respective electronic devices. Batches of data are read from the successive electronic devices and displayed on the display 5a of the tester 5. The thus-read batches of data are compared with normal data previously stored in the tester 5 and are suitably processed such that the display 5a displays the code indicative of the faulty electronic device.
In this known fault diagnosis system, the functions of the diagnosis tester 5 are independent from the self-diagnosis function of each of the electronic devices 1a, 1b and 1c. The user cannot be informed of the occurrence of a fault and cannot determine the portion where the fault exists, unless he operates the keys 5b after connecting the tester 5 to the connector 4, even when at least one of the electronic devices 1a, 1b and 1c is outputting a defect detection signal and the code signal representing the faulty portion. For example, it cannot be determined from the code representing device 1a whether the fault resides in its sensor 2a (or 2b or 2c) or in its actuator 3a (or 3b or 3c) upon detection of the fault by its self-diagnosis function.
In general, fault diagnosis requires not only the identification of the faulty portion but also an analysis of the cause of the fault. Fault analysis requires various data such as identification of the faulty part, when the fault took place, under what conditions the fault occurs, and so forth. This in turn requires that one or more engineers who are skilled in fault diagnosis, in addition to the test driver, be present in an automobile during a test drive, because there are so many items to be checked during a test drive. For instance, it is necessary to watch the state of the warning lamp to check under what conditions the warning lamp lights up, and also to read the number of blinks exactly to identify the faulty part, while correctly manipulating the diagnosis tester in accordance with a predetermined sequence or program.
Thus, the known fault diagnosis system requires a plurality of skilled persons at one time, and an impractically long time for determining the faulty portion and the cause of the fault.